1. Field of the Invention
The present invention relates to a ferrite-core housing case for housing a ferrite core which is to be attached to a flat cable to suppress noises propagating through the flat cable, an anti-noise component in which a ferrite core is housed in such a case, and a wire harness and an electronic apparatus to which such an anti-noise component is attached.
2. Discussion of the Background
Conventionally, an anti noise measure is taken by using a ferrite core in a cable connecting various electronic apparatuses. Such a cable includes a flat cable. Also in a cable of this kind, an anti noise measure is taken in the same manner.
As a ferrite core used for an anti noise measure in a flat cable, used is a flat O-like (flat ring-like) ferrite core 1 such as shown in FIG. 6 and having a slit-like hole 2 through which a flat cable FC is to be passed. Such a ferrite core 1 has the illustrated integral type structure or a split type one in which split core halves are butted against each other to form a flat O-like shape.
This ferrite core 1 is used while the flat cable FC is passed therethrough. When the cable is passed and no further measure is taken, the ferrite core is moved along the cable. When the ferrite core 1 is moved on the flat cable FC, there arises a fear that the ferrite core 1 collides with the interior of an apparatus in the vicinity of the place where the ferrite core 1 is attached, and the apparatus or the ferrite core 1 is damaged. Furthermore, a desired noise reduction effect may not be attained depending on the place of the flat cable FC.
These problems can be solved by fixing the ferrite core on the flat cable. This can be implemented by a method in which the ferrite core is fixed to the flat cable by means of an adhesive agent or an adhesive tape, or that in which the ferrite core is fixed to an apparatus housing or a circuit board which is in the vicinity of the core, by means of an adhesive agent or an adhesive tape.
However, these methods are low in working efficiency. As a countermeasure, a component 5 such as shown in FIG. 7 and for fixing positions of a ferrite core and a flat cable has been proposed (produced by TOKIN Corporation, product name: FPD-CL-1 camp). The component 5 is characterized in that it is attached to a side face of each of the end portions of a ferrite core 1 and can be fixed to an apparatus housing or a circuit board 10 by, for example, fastening of a bolt 7 and a nut 8 with using a hole 6 formed in the component 5.
In the case where the ferrite core 1 is to be attached to an apparatus housing or a circuit board by using the component 5 of FIG. 7, however, the component is attached to the ferrite core 1 and the fixing work must be then conducted while pressing the ferrite core 1 and the component 5 by a hand so as not to separate them from each other. When the ferrite core 1 is once fixed onto the circuit board and the core is to be then detached therefrom, the ferrite core 1 can be detached from the circuit board, only after the whole of the assembly is detached therefrom.
In order to solve these problems, the assignee of the present application has proposed an anti-noise component for a flat cable in U.S. patent application Ser. No. 09/261,228. The proposed anti-noise component is characterized in that a split type ferrite core 1 (configured by butting split ferrite core halves 1a and 1b against each other) which is to be attached to a flat cable FC is housed in an openable and closeable case 15 (configured by coupling split case halves 15a and 15b to each other), and a coupling portion 18 for fixation to a circuit board is formed on a bottom portion of the case, whereby attachment and detachment of the ferrite core 1 is facilitated, and the ferrite core 1 is prevented from being damaged with a shock, and easily attached to an apparatus, a circuit board, etc.
In the anti-noise component shown in FIG. 8, the ferrite core 1 is pressed by a spring portion 16 formed in a center portion of the upper face of the split case half 15b in order to, when the case 15 is closed, prevent the ferrite core 1 housed therein from being moved in the case. When the ferrite core 1 is moved in the case 15, the ferrite core 1 bumps against the case 5 to produces acoustic noises. This is not preferable.
In the component disclosed in U.S. patent application Ser. No. 09/261,228, as shown in FIG. 8, the spring portion 16 is disposed in the center portion of the upper face of the split case half. Because the split case halves 15a and 15b have a flexibility of a certain degree, the disposition of the spring portion at such a position causes the force of the spring portion 16 pressing the ferrite core 1 to be applied also to the case 15, thereby raising the split case half 15b. This raised state is shown in FIG. 9. When the ferrite core 1 is housed, the upper face of the split case half 15b which is originally in the state indicated by the solid line is raised in the center portion of the case half to warp the case 15. When the case 15 is warped, the force of the spring portion 16 pressing the ferrite core 1 is reduced, so that the ferrite core 1 cannot be sufficiently fixed. The warped state of the case 15 impairs the appearance of the case.
Also in the case where two spring portions 17 are disposed in a center portion of the upper face of the split case half 15b as shown in FIG. 10, there arises a phenomenon in which, when the ferrite core 1 is housed, the center portion of the case half is raised as indicated by the broken lines to warp the case 15.
The force of the spring portion is enhanced by increasing the inclination angle of the spring portion with respect to the inner face of the case. In accordance with enhancement of the force, also the force of raising the split case half is increased so as to further warp the case.